Although, after the art of agriculture had been developed, mankind was gradually relieved from its past dependence on the tree as a means of support, it nevertheless continued to be regarded with veneration as an emblem of creative power or of productive energy. Among the traditions and monuments of nearly every country of the globe are to be found traces of a sacred tree--a Tree of Life. In various countries there appear two traditional trees, the one typical of the continuation of physical life, the other representing spiritual life, or the life of the soul. After the age of pure Nature-worship had passed, however, and serpent, fire, and phallic faiths had been introduced, the original signification of the tree, like that of all other religious emblems, became considerably changed. Through its energies, or life-giving properties, existence had long been maintained, and for this reason, as has already been observed, it became an object of veneration; but, after the reproductive power in man had risen to the dignity of a supreme God, the tree, to the masses of the people, became a symbol of the physical, life-giving energy in mortals and in animals. In other words, it became a phallic emblem representing the continuation of existence, or the power to reproduce or continue life on the earth. As a religious symbol it became the traditional Tree of Life. The tree, like nearly every other object in nature, was and still is, in various parts of the world, either female or male, and all ideas connected with it are sacred and closely interwoven with sex. The extent to which trees have been venerated in past ages seems to be little understood, and there are doubtless few persons, at the present time, who would willingly believe that all along the religious stream, from its source to its latest developed branches, are to be observed traces of this ancient worship, which, in its earliest stages, was simply a recognition of Nature's bounties. Barlow, in his work on Symbolism, says that "the most generally received symbol of life is a tree--as also the most appropriate." Again the same writer observes: "Besides the monumental evidence thus furnished of a sacred tree, or Tree of Life, there is an historical and traditional evidence of the same thing, found in the early literature of various nations, in the customs, and popular usages."(6) As tree- and sun-worship, or the adoration of Nature's processes, finally became interwoven with phallic faiths, its history can be understood only after these later developments in the religious stream have been examined, or after the true significance of the serpent as a religious emblem, and the various ideas connected with the traditional Tree of Life, have been exposed. 6) Essays on Symbolism, p. 84.